TO THE REPORTERS who covered the Nixon Administration, they were known with a mixture of resentment and grudging respect as the German shepherds, the Berlin wall and - with Henry Kissinger - the Teutonic Trio.

Harry Robbins Haldeman was always coupled with his fellow Nixon aide John Ehrlichman. Both served as senior aides to President Nixon in the White House, and both served prison terms for their parts in the Watergate affair. They were very different men in many ways. Ehrlichman was a lawyer from Seattle, whose uncle, a real estate investor, was one of the richest men there. Haldeman was an advertising executive with the J. Walter Thompson agency. Ehrlichman is shambling and gregarious; Haldeman's trademarks were his ramrod posture, military crewcut and tight lips.

Yet it was understandable that their names were as closely identified, one journalist said, as Laurel and Hardy or Rosencrantz and Guildenstern. They were both Christian scientists. They were both conservatives. And they were both unconditional loyalists at the court of Richard Nixon.

Both of Bob Haldeman's grandfathers were successful small businessmen in Indiana. Both moved to southern California; both were isolationist Republicans. Haldeman's father inherited a pipe and building supply company which collapsed in the Depression. In 1933, he started up again, selling heating and air- conditioning units. The second business prospered and Bob Haldeman grew up first in Beverly Hills and then in the San Fernando Valley. After doing poorly at a public high school, he was sent to a private school which imbued him with a lifelong respect for discipline and self-discipline.

Just too young to fight in the Second World War, Haldeman was active at the University of California at Los Angeles on the Interfraternity Council. Among other things he organised a campaign for campus-wide election of the editors of the student newspaper because he was afraid that the Daily Bruin had fallen into the hands of Communist sympathisers.

It was natural for a young man from Haldeman's conservative background to admire Richard Nixon, the young politician from southern California who became a hero to conservatives as a result of his prosecution of the Hiss Communist espionage case. However Haldeman went to work in advertising, first briefly for Foote Cone & Belding, and then for the J. Walter Thompson agency, and did not meet Nixon until 1951.

His talent as an advertising man lay not on the creative side, but as an organiser. He worked on a number of accounts, among them Disneyland, the soft drink 7-Up, a roach poison called Black Flag, and Snarol, to kill snails. By the 1960s he had become one of the vice-presidents of the agency in Los Angeles. By then, however, he had discovered another career that was to bring him both triumph and disaster. In 1956 Haldeman worked for Nixon as an 'advance man' in his campaign.

Haldeman's hostility towards the press was deepened by his experience with the Nixon election campaigns in 1956, 1960 and for the governorship of California in 1962. It was Haldeman who provoked Nixon into his famous outburst at the press ('You won't have Nixon to kick around'). He had been watching the metaphorically baying for Nixon's blood on a television set in the candidate's suite, and worked Nixon up into the mood that led to the famous outburst.

When Nixon entered the White House in 1968 he brought Haldeman with him as his chief of staff, accompanied by a whole phalanx of dapper advertising men from Los Angeles. Haldeman soon imposed his authority as the sternest administrator ever seen on a White House staff. Instead of the freewheeling atmosphere of the Kennedy and Johnson years, Haldeman barked orders and demanded instant obedience.

He understood that Nixon liked to be alone. Haldeman was literally the guardian of his door, ruthless in excluding all the President did not need to see. This made enemies in Washington, a city where access is the lifeblood of careers, for Nixon and even more for Haldeman. He succeeded in insisting that even cabinet secretaries could not see the President except with his, Haldeman's, permission. In the end even John Mitchell, Nixon's campaign manager and Attorney-General, could enter the Oval Office only with Haldeman's permission.

In his memoirs, Haldeman wrote that he was 'no worshipper' of Richard Nixon, and said he had no interest in working for him 'except in his political endeavours'. This weekend, however, Nixon remembered Haldeman as 'a man of rare intelligence, strength, integrity and courage', and said he played an 'indispensable role' in his administration. Unfortunately for Haldeman, he played a crucial part in the attempt to cover up the long series of illegal or unseemly actions that came to be known as 'Watergate'.

Three days after burglars hired by the Committee to Re-elect the President were arrested in the Democratic national committee's office, Haldeman and Nixon discussed how to conceal White House involvement in the crime. The 18- minute gap on the tape recording of that conversation, erased by the President's secretary, came to be called the 'smoking gun' in the Watergate affair; its revelation led to the President's resignation. Haldeman was also taped discussing with Nixon how he might use the Central Intelligence Agency (in breach of American law) to throw the Federal Bureau of Investigation off the scent. Haldeman was found, further, to have controlled a dollars 350,000 'slush fund' used to pay the living expenses of some of the Watergate burglars.

On 30 April 1973 Haldeman and Ehrlichman and other senior Nixon aides were compelled to resign from the White House staff. Haldeman was later convicted of obstruction of justice, conspiracy to obstruct justice, and lying to the FBI and to a Grand Jury. He served 18 months of a two-and-a-half-to-eight-year term in a Federal Penitentiary.

After his release Haldeman went home to California and went into the office- and hotel-developing businesses. When he died he was the owner of a chain of steak-houses in Florida.